Side brushes of the above type have been traditionally constructed by means of a base element, made for example from a flat plywood panel and having a radially sufficiently wide zone in its outer periphery extending from the center of the base element and provided with pairs of holes in an inclined position. Providing this type of side brush with bristles is effected by threading the bristles in one hole and out of the other, which is followed by clamping the bristles in place for example with a plywood or metal plate fastened to the back of the base element. A downside in this type of solution is particularly the inconvenience of its manufacture, since, first of all, a multitude of paired holes must be drilled in the base element, whereafter the bristles threaded therein must be further clamped in position by means of a back cover. Another notable drawback is that a side brush of the above type is a disposable item, because dismounting bristles from a base element is not economically viable but, instead, replacing the entire side brush with a new one is more convenient.
On the other hand, the implementation of a so-called cassette principle in the above-mentioned context is presently known. This type of side brush solutions include a base element, which is fabricated e.g. of a rather thin metal sheet by form-bending, such that it is provided with a coupling system in a position inclined relative to the mounting plane of a side brush, which enables a detachable anchoring thereto of bristle segments manufactured in a prefabrication stage. The bristle segments used in this instance are currently manufactured in such a way that the bristles are bound together at one end thereof e.g. by a form-bendable base element of sheet metal, which is slippable in slots functioning as a coupling system. One optional solution in this respect is e.g. such that the base element is provided with holes through which the bristles are threaded, whereafter the base element's back face is fitted with an appropriate clamping plate for securing the bristles in place. Another alternative solution is described in U.S. Pat. No. 3,678,530, wherein the frame member holding each bristle segment together is constituted by a three-component frame structure, which is then secured to the base element of a side brush.
This type of solutions, based on a so-called cassette principle, are not currently very functional either, firstly due to the fact that the fabrication of bristle segments is laborious and expensive because, first of all, the positioning of bristles in place requires an unacceptable amount of manual labour, in addition to which the bristles must, on the other hand, be manufactured with a quite high dimensional precision in order to fit the same in a respective coupling system by applying a force as little as possible. In practice, however, this causes all sorts of problems in an installation process because of rather large manufacturing tolerances existing in this type of construction for natural reasons. On the other hand, solutions of the above type do not enable recycling or the reuse of bristle segments included therein without unacceptably laborious/expensive dismounting operations, which is why it is generally necessary to ultimately discard such material to a waste disposal site. In addition, as a result of metal constructions used in association with arrangements of the above type, the base structures of bristle segments become unacceptably massive, wherefor the coupling and bracing systems included in a sweeping machine must also be of a highly robust design.
Another solution has been disclosed in U.S. Pat. No. 4,236,269, wherein the base element of a vertical axis brush comprises a flat plate structure, which is integrally provided with a coupling system for attaching bristle segments thereto in a snap fit fashion. In this instance, the coupling system consists of clamps formed in the base element, between which the U-shaped bristle segments are attachable. A problem with this type of solution lies particularly in the fact that there is no way of providing a sufficiently reliable clamping for the bristle segments, since no actual locking can be implemented in this discussed solution. For this reason, the positions of bristle segments are also somewhat unstable in the vertical axis brush, firstly as a result of manufacturing tolerances in the bristle segments' U-shape and secondly because the clamps included in the plate or disc are subject to bending in extended use. This aspect in itself is of major importance in terms of holding a vertical axis brush together. Thus, in practice, it is not possible to assemble a sufficiently reliable side brush with the discussed type of solution.